UNTERPREMSTAETTEN, Austria--(BUSINESS WIRE)--ams AG (SIX:AMS), a leading provider of high performance analog ICs and
sensors, today introduced an example design for lithium pedelec/e-bike
batteries which implements accurate cell monitoring and balancing
without the need for a microcontroller in the Battery Management System
(BMS).

Battery pack and pedelec manufacturers which use the design will benefit
from valuable bill-of-materials (BoM) cost savings and a simpler circuit
design, compared to batteries in production today.

The ams design is for a 48V pedelec battery consisting of up to 14
lithium-ion cells. It uses two AS8506 smart cell monitoring ICs, with
few supporting components, to monitor the temperature and voltage of up
to seven cells each and to implement passive balancing of the cells when
charging.

By contrast, conventional BMS designs in pedelecs use dumb voltage
monitoring ICs to measure the voltage and temperature of cells,
reporting the values to a dedicated battery management microcontroller
via a serial communications link. The MCU is required to control safety
and protection functions (over- and under-voltage and over-temperature
shut-down) and cell balancing.

The AS8506 from ams, however, includes built-in logic functions for
controlling cell safety, protection and balancing. These functions can
easily be configured by the user, with the settings saved in an on-board
OTP memory. The device also features integrated MOSFETs for use in
passive cell balancing operations. During charging, each cell’s voltage
is compared to a user-programmable reference voltage threshold. Up to
100mA may be discharged through the MOSFET from any cell exceeding the
threshold, until all cells have reached the threshold and the battery
module is fully charged.

This architecture, in which battery monitoring and cell balancing
operations are implemented inside the AS8506 voltage-monitoring device,
dispenses with the dedicated MCU required in conventional pedelec
battery designs. When an AS8506 detects an over- or under-voltage or
over-temperature condition, an interrupt signal is transmitted to the
pedelec’s motor controller IC to complete the required safety shut-down
operations.

‘Battery lifetime, safety and run-time strongly affect consumers’ choice
of pedelec, but so does cost,’ said Bernd Gessner, Vice President and
General Manager of the automotive business unit of ams. ‘The
controllerless reference design from ams helps pedelec manufacturers
meet consumer demand by providing outstanding safety and battery
performance, but in a simpler and lower-cost architecture than has
previously been available.’

The reference design can be used in any pedelec or e-bike battery
containing up to 14 lithium-ion cells. It can also be extended to
supervise more than 14 cells by daisy-chaining additional AS8506 ICs as
required.

The reference design files are available on request from ams.

Price & Availability

The AS8506 cell monitoring IC is in volume production now. It is priced
at $9.10 for 1,000 pieces.